NEW BEDFORD — New Bedford City Hall was evacuated Friday morning following a bomb threat.

Mayor Jon Mitchell said the original threat was received Thursday night, and was investigated by police. He said another threat was received Friday morning.

The building was searched and bomb-sniffing dogs were brought in to look for an explosive devices or threatening objects.

"There were threats that were made concerning City Hall this morning," Mitchell said. "The police were promptly notified and responded, as the fire department, and they spend considerable time checking the building with bomb-sniffing dogs."

Employees stood out on the sidewalk awaiting the all-clear to go back to work as authorities searched City Hall.

"They saw nothing visually, and the dog didn't notice anything out of the ordinary," Mitchell said. "They've said the building is clear, so we'll be getting back to business as soon as we can."

The scene was cleared and employees returned to the building shortly after 11 a.m.

Mayor Mitchell declined to get into specifics of what the threat was or how it was received, citing an active investigation. He said there will be extra security around City Hall for the forseeable future.

"There will be extra police, a beefed-up police presence from the end of the day until further notice," he said. "When to reduce that presence will be further determined by the police department."

Tim Dunn contributed to this report.