Since the terrorist attacks in Mumbai 10 days ago, speculation has been rife about the birthplace of the lone surviving gunman, Ajmal Amir Kasab. India and Pakistan have clashed over reports that he came from the Punjab. Saeed Shah, after spending days travelling throughout the region, tracked down the killer's home - and his grandfather - and found conclusive proof of his identity

The little house was certainly that of a poor family, with a courtyard to one side and a small cart propped up in one corner. The old man and middle-aged woman who answered the door were not the owners. No, they insisted, the owners were away.

'They've gone to a wedding,' said the old man, identifying himself as Sultan. He was, he said, Amir's father-in-law. So, that would make him Ajmal's grandfather? At last, it seemed, this was the right place.

It had taken days to get to Faridkot, a small, dirt-poor village in Pakistan's Punjab province. More than a week after the arrest of the only Lashkar-e-Taiba terrorist taken alive during the terror strike on Mumbai, so little was still known about him. His name, for instance. Was he Mohammed Amin Kasab, Azam Amir Kasav? Or was he Mohammed Ajmal Amir? The name Kasai in fact means he would hail from a butcher community - that would be his caste. But it was recorded as Kasav, then later Kasab. The discrepancies reportedly stemmed from the fact that the Mumbai police officers who first questioned him were Marathi speakers and unable to communicate with the south Punjab resident in anything other than Hindi patois.

And where exactly was he from? Faridkot is what he told his interrogators, but this is a common village name. There were four candidates in the Punjab region.

Days of trying to establish which was the right one had led to a Faridkot near the Indian border, outside a town called Depalpur. The nearest city was Okara. It seemed to fit. And it was at this Faridkot that Ajmal's father was believed to live.

Initially villagers were unhelpful. No, said those approached, there was no one known here of that name. Even shown a photograph of Ajmal taken during the Mumbai siege, all swore they did not recognise him. The mayor was clear. 'There is a man who came to see me called Amir Kasab, who was worried,' said Ghulam Mustafa Wattoo. 'He told me that the Ajmal on the news was not his boy. That boy's gone away to work. There's no extremist network here.'

Was this another dead end?

As the villagers were questioned, the confusions appeared to multiply. Finally the name Mohammed Ajmal Amir, son of Mohammed Amir Iman, who ran a food stall, emerged.

At other Faridkots, including one near the town of Khanewal, villagers had been friendly and helpful, proffering tea as they shook their heads. 'No. Not from here,' they said. For a while, it appeared that this Faridkot would also prove a wasted journey. The mayor said there had been no local police investigation, suggesting that the authorities did not view this place with suspicion. But, over time, inconsistencies in the villagers' accounts heightened suspicion that this was the place. 'He [Amir] has lived here for a few years,' said one villager, Mohammad Taj. 'He has three sons and three daughters.'

Noor Ahmed, a local farmer, said: 'Amir had a stall he pushed around, sometimes here, sometimes elsewhere. He was a meek man, he wasn't particularly religious. He just made ends meet and didn't quarrel with anyone.'

Still the picture was confusing. While sometimes confirming that Amir did live in the village, and had a son called Ajmal, on other occasions locals claimed to know nothing.

Finally one villager confirmed what was going on: 'You're being given misinformation. We've all known from the first day [of the news of the terrorist attack] that it was him, Ajmal Amir Kasab. His mother started crying when she saw his picture on the television.'

Attempts to meet Amir, the father, however, were not to be successful. Villagers eventually told us that he and his wife, Noor, had been mysteriously spirited away earlier in the week.

'Ajmal used to go to Lahore for work, as a labourer,' continued the villager who feared being named. 'He's been away for maybe four years. When he came back once a year, he would say things like, "We are going to free Kashmir."'

Wresting the whole of Kashmir from Indian rule is Lashkar-e-Taiba's aim. Ajmal had little education, according to locals. But it is still unclear whether he was radicalised in the village or once he had left to work elsewhere.

It is said that from the age of 13 he was shuttled between his parents' house and that of a brother in Lahore. If he did indeed speak fluent English, as claimed in Indian press reports, he would have had to have learnt that after he left the village.

But the villager who turned whistleblower said that local religious clerics were brainwashing youths in the area and that Lashkar-e-Taiba's founder, Hafiz Sayeed, had visited nearby Depalpur, where there were 'hundreds' of supporters. There was a Lashkar-e-Taiba office in Depalpur, but that had been hurriedly closed in the past few days. The Lashkar-e-Taiba newspaper is distributed in Depalpur and Faridkot. Depalpur lies in the south of Punjab province, an economically backward area long known for producing jihadists.

Shown a picture of Ajmal, the villager confirmed that he was the former Faridkot resident, who had last visited the village a couple of months ago at the last festival of Eid.

Some locals have claimed that this Faridkot, and another poor village nearby called Tara Singh, are a recruitment hotbed for Lashkar-e-Taiba, the militant group accused of carrying out the Mumbai attack. On the side of a building, just outside Faridkot, is graffiti that says: 'Go for jihad. Go for jihad. Markaz Dawat ul-Irshad.' MDI is the parent organisation of Lashkar-e-Taiba. In Depalpur, a banner on the side of the main street asks people to devote goatskins to Jamaat ud Dawa, another MDI offshoot.

Tara Singh is home to a radical madrasa - Islamic school - and there is another hardline seminary in nearby Depalpur. The nazim (mayor) of Tara Singh, Rao Zaeem Haider, said: 'There is a religious trend here. Some go for jihad, but not too many.'

Some reports emerging in India suggest that Ajmal may have joined Lashkar -e-Taiba less because of his Islamist convictions but in the hope that the jihad training he would receive would help to further the life of crime upon which he had already embarked. But once inside Lashkar's base, his world-view began to change.

Here, films on India's purported atrocities in Kashmir and heated lectures by fiery preachers led him to believe in Lashkar's cause. It has also been said that, when he was chosen for the Lashkar basic combat training, he performed so well that he was among a group of 32 men selected to undergo advanced training at a camp near Manshera, a course the organisation calls the Duara Khaas.

And finally, it seems, he was among an even smaller group selected for specialised commando and navigation training given to the fedayeen unit selected to attack Mumbai.

The authorities may now attempt to deny that Ajmal's parents live in Faridkot, but, according to some locals, they have been there for some 20 years. But by the end of our visit, a crucial piece of evidence had been gained. The Observer has managed to obtain an electoral roll for Faridkot, which falls under union council number 5, tehsil (area) Depalpur, district Okara. The list of 478 registered voters shows a 'Mohammed Amir', married to Noor Elahi, living in Faridkot. Amir's national identity card number is given as 3530121767339, and Noor's is 3530157035058.

That appears to be the last piece of the jigsaw. A man called Amir and his wife, Noor, do live in Faridkot, official records show. They have a son called Ajmal.

Following our last visit to Faridkot, the mayor, Wattoo, announced via the loudspeaker at the mosque that no one was to speak to any outsiders. By yesterday, Pakistani intelligence officials had descended in force on Faridkot. Locals, speaking by telephone, said a Pakistani TV crew and an American journalist had been roughed up and run out of town. It appeared that the backlash had begun.

The key numbers

10 The number of people India says took part in the attack on Mumbai

1 Survivor from the militant group

2 Indians arrested on Friday in Calcutta suspected of handling phone cards used by the Mumbai attackers. Sources say later that one may be an undercover agent

163 Amended death toll after the massacre. At one point it was believed to have been as high as 195

204 Number of boats India will deploy to prevent future attacks