Holyoke Center and Au Bon Pain were evacuated yesterday afternoon due to a bomb scare caused by a "suspicious object" that firefighters later determined to be a fuse box.

After the area was deemed safe, however, the Cambridge Fire Department received a telephone bomb threat. The caller said the bomb was located somewhere in the building and gave officials a time frame in which it would detonate, according to Deputy Fire Chief John J. O'Donoghue. He could not release the actual time of the call.

O'Donoghue said the building would remain evacuated for the rest of the evening because of the second bomb threat.

Fire officials had blocked off the entire sidewalk in front of Holyoke Center at about 4:15 p.m. after receiving a call from center employees re porting the presence of an unknown black box.

The area remained blocked off until the "incidents team," or bomb squad, determined the object was an electrical box. The evacuation lasted approximately 30 minutes.

O'Donoghue speculated that the box was "probably just an electrical box that an electrician left behind by mistake."

"We didn't know what was going on for a while," said Terry C. Sullivan, head teller at Cambridge Trust. She said fire officials did not tell employees and customers that there was a bomb scare, although they were told to evacuate quickly.

Sullivan added that no one was panicked and that customers even wanted to finish their transactions before leaving the bank.

Approximately three fire trucks and several police cars were on the scene