More than 500 people have been taken to hospital with suspected food poisoning after eating bánh mì sandwiches from a shop in southern Vietnam.

Twelve of them, including two boys aged between six and seven, are in a critical condition.

The bakery, which is based in Dong Nai province, has been temporarily shut down.

It is believed the sandwiches may have spoilt as a result of the current heat wave.

An initial inspection of the bakery revealed that it did not meet food safety standards.

Bánh mì is a traditional Vietnamese sandwich consisting of a French-style baguette stuffed with cold meats, pâté and vegetables.

On Monday, Long Khanh Town authorities confirmed that at least 560 people had fallen ill after consuming sandwiches from Bang bakery in Long Khanh city on 30 April.

They also stated that 200 people had since been discharged.

The bakery, based on Tran Quang Dieu Street, sells about 1,100 of the sandwiches every day, according to local authorities.

The number of cases of suspected food poisoning has steadily risen each day, say local hospital reports.

Symptoms included diarrhea, vomiting, fever and severe abdominal pains.

One Vietnamese newspaper, Health and Life, spoke to one woman whose three children were being treated at the intensive care unit at Dong Nai Children's Hospital.

Tran Ngoc Phuong told the paper she bought three sandwiches for her children with extra meat. Within 24 hours, they all began showing symptoms of food poisoning.

The region's Health Department said on Sunday that blood tests of some of those who had become critically ill showed the presence of E. Coli - a bacterium that typically appears in fresh produce including beef, cheese and fruit.

According to Tuoi Tre News, local health workers have taken a sample of the banh mi to a lab for further testing.

Police say they have launched an investigation into the cause of the food poisoning. (BBC)