British police closed at least 11 Tesco supermarkets across the country Saturday because of a security alert, authorities said.

The manager at a Tesco in Barrhead, near Glasgow, told Britain's Press Association that staff were sent home around 12:30 p.m. (1330 GMT) after a power failure. But an unidentified employee at a neighboring shop said police had told him there had been a bomb threat.

Police in Hertfordshire, where Britain's largest supermarket has its headquarters, said no one had been hurt and that the move was a precaution. Police did not immediately give further details.

"Police are investigating a series of incidents in a number of locations across the country involving Tesco stores," a Hertfordshire police spokeswoman said on condition of anonymity in line with force police. "These stores have been temporarily closed as a precaution for public safety."

Tesco said the police had responded to a number of incidents.

"Police are investigating and so we are unable to comment further," she said on condition of anonymity in line with company policy. "As always, at all times customer welfare is our priority."

Police said the closures affected stores in London, other locations in England, and Scotland and Wales.

A spokesman for South Wales police said the Tesco store at Riverside, Port Talbot, had been closed since Saturday afternoon and said officers would remain at the store for as long as necessary.