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."