Manila: A loud explosion was heard on the grounds of the Philippine presidential palace on Monday, Philippines television station ANC said.
The cause of the blast which rocked the presidential palace on Monday was not immediately known and there were no known casualties.
Witnesses said a green garbage can was shredded by the blast, which brought government workers from their offices.
The explosion on the grounds of the Philippine presidential palace on Monday was probably caused by chemicals in a trash bin set off by a lit cigarette, not a bomb, the head of security told reporters later.
"Nobody was injured," press undersecretary Isabel de Leon told reporters, adding President Gloria Macapagal Arroyo was
inside the palace at the time.
The army tightened security on Sunday after finding a bomb in its top military academy, one of the alleged targets of a plot to overthrow and possibly kill President Gloria Macapagal Arroyo.