The rescue operation at the collapsed building site in Dhaka, Bangladesh took a dramatic turn on Friday afternoon when a fire service rescue team located a large group of survivors in an air pocket on the third floor of the wrecked structure.

The building, which came down on Wednesday was "stacked like slices of bread", said Manzur Ahsan, a fireman. Unable to access the lower floors, army engineers had started tunnelling into the wreckage from an adjoining building.

"We broke through on Friday afternoon and immediately heard cries for help," said Ahsan. "Some survivors struck the concrete with loose bricks to attract attention."

The anxious crowd gathered outside broke into cheers as, one by one, 24 people were brought out alive by army and fire service personnel. By evening, more survivors had been dug out, bringing to 100 the number of people rescued on Friday. A total of 2,300 people have been rescued from the rubble. Rescuers fear hundreds may still be inside.

Among the survivors on Friday was Rehana Begum, a seamstress who worked at the Ether Tex garment factory on the third floor. Even though her left arm was broken, she knew she was among the lucky ones.

"I felt I was buried alive," Begum said through her tears. "I never thought I'd see sunlight again."

Meanwhile pressure was mounting on the government of Bangladesh amid anger at senior officials' reaction to the deaths this week of hundreds of workers in the collapse of the factory making clothes for western companies.

The death toll rose to well over 300 on Friday and was expected to continue to climb as bulldozers were brought in to clear the rubble of the eight-storey Rana Plaza complex in the Savar industrial zone on the outskirts of the capital, Dhaka.

Western retailers including Primark and Matalan have said they had been supplied by factories in the complex.

Up to 3,000 workers may have been in the building when it collapsed at 9am on Wednesday morning. Rescue efforts have relied heavily on volunteers using crowbars, picks and bare hands to clear debris and reach survivors. Firefighters and military personnel were forced to halt operations on Fridayfor two hours after relatives angry at the slow pace clashed with police and teargas was fired in response.

Volunteers were seen holding placards calling for drills, surgical masks and other items. "We're struggling for supplies. We need more help from the authorities," said Mehdi Hassan, a volunteer.

"The police barred us from going near the spot and when we protested, starting hitting us with sticks," said Majid Mia, who had been waiting outside the site for two days hoping for news of his missing daughter, Minara. "When some men pelted the police with stones, they fired teargas," he added.

Elsewhere in Dhaka on Friday, angry garment workers protesting about the Savar tragedy damaged an estimated 100 vehicles in the Mirpur, Rampura and Badda areas while thousands more downed tools. Iqbal Hossain, in charge of Badda police station, said demonstrations had suddenly turned violent.

"We're trying to talk to garment labour leaders to calm the situation," he said.

The tragedy is potentially damaging for the ruling Awami League of the prime minister, Sheikh Hasina.

Local media have criticised statements by Hasina and the home minister, Mohiuddin Khan Alamgir. On Wednesday, Hasina said on TV that the building had been evacuated but some people were trapped after "they went back for their things". Survivors say workers were ordered into the building on Wednesday even though large cracks had appeared in the wall the previous day.

Alamgir was ridiculed on social media after he told the BBC that the building may have collapsed after opposition activists enforcing a general strike "pushed at the gate and columns of the building".

On Friday Hasina bowed to popular demand and ordered the arrest of the owner of the building, Sohel Rana, who is on the run, and the owners of the five garment factories. Rana is a local politician with the ruling Awami League and is accused of exploiting his political influence to flout planning regulations to build the complex six years ago.

"The prime minister has ordered the top officials of the law enforcement agencies to arrest the owners of Rana Plaza and the garment factories operating in the building immediately," said a spokesman for the prime minister.

Rana is also accused of ignoring repeated warnings about the building and forcing factory employees to return to work despite fears that a collapse was imminent.

Officials said Rana was told of dangerous cracks in the building on Tuesday. While a bank in the building closed on Wednesday because of the warnings, the five clothing companies told their workers there was no danger, industry officials said.

"We asked the garment owners to keep it closed," said Mohammad Atiqul Isla, president of the Bangladesh Garment Manufacturers and Exporters Association (BGMEA).

The booming garment trade is a major foreign exchange earner in Bangladesh and employs about 4 million people. Most of the exports – 60% – goes to Europe while the US takes 23% and Canada 5%.

All political factions actively court the powerful lobby of garment manufacturers and activists say this is what hinders efforts to improve conditions in factories.

A series of accidents at garment factories have claimed hundreds of lives. Only months ago a blaze in a factory without proper fire escapes killed 112.

Bangladesh has been hit by political turmoil in recent months following verdicts on alleged war crimes during the brutal 1971 war of independence by a new tribunal set up by the government. The opposition Bangladesh Nationalist party and Islamist groups have organised vast demonstrations in protest. A campaign supporting the tribunal and calling for harsher sentences has waned in recent weeks.

The political loyalties of the owner of the collapsed complex will give further ammunition to the opposition. On Friday there were further demonstrations and political violence in Bangladesh.

Elections are due later this year and analysts say further instability is likely.