Greek security officials are scrutinising courier and postal services after a letter bomb attack on Thursday that left former prime minister Lucas Papademos in hospital.

Papademos, who underwent surgery after sustaining injuries to his leg, stomach and chest, opened the envelope as he was being driven home in Athens. Two Bank of Greece employees were also wounded.

As prime minister, Papademos had navigated Greece through austerity measures over a six-month period beginning in late 2011.

A statement from the Greek health ministry said he was being treated for wounds in his right thigh and upper body.

The national media on Friday said the focus was on the letter’s trail and how it came to arrive in his hands after being sent to his home. Earlier, it had been thought the missive had been posted to the Academy of Athens, which is headed by the respected economist, who is also a former vice-president of the European Central Bank.

Addressing reporters after visiting Papademos in hospital on Friday morning, Antonis Samaras, who succeeded him as prime minister, said: “The letter arrived at his home after undergoing checks which did not detect the explosive material.”

Counter-terrorism experts fear other booby-trapped parcels may have slipped into the system. “They are clearly becoming much better in their tactics and more innovative,” Mary Bossi, professor of international security at Piraeus University, told the Guardian.

“The government was meant to have invested in expensive machinery to detect explosives but clearly it is unable to do that with very small amounts. For [the attackers] this is clearly a triumph.”

Suspicions have fallen on a homegrown group, the Conspiracy of the Cells of Fire, who recently claimed responsibility for sending letter bombs to the German finance ministry and the Paris offices of the International Monetary Fund.

A police officer secures the area around Papademos’ car in Athens. Photograph: Costas Baltas/Reuters

All were intercepted, although in the case of the package sent to the IMF a female employee was wounded as she opened the parcel in March.

Two other people, including Papademos’s driver, were also injured in Thursday’s early evening attack. All three were described by doctors as being in a stable condition.

Anti-austerity groups have vowed to strike at the establishment with figures behind the handling of the country’s crisis feared to be prime targets.

“I unequivocally condemn the attack against Lucas Papademos,” the Greek prime minister, Alexis Tsipras, tweeted. “I wish a speedy recovery to him and the people who accompanied him.”

Bossi said: “What has happened is a very worrying development. Quite clearly, as others were also injured in this attack, they don’t care if there is collateral damage. Those who should be, are not being vigilant enough. The next time someone will be murdered.”