Belfast, Northern Ireland (CNN) -- Police in Northern Ireland on Tuesday were investigating two pipe bombs left at a housing estate in Belfast.
One of the bombs exploded around 8 p.m. (4 p.m. ET) Monday night. There were no reports of injuries, and security forces defused the second device, found a short time later, police said.
Residents were evacuated and housed at a local community center until they were allowed to return Tuesday morning, the Police Service of Northern Ireland said.
The estate is located in west Belfast, a Republican part of the city.
The main political party in the district, Sinn Fein, said the pipe bomb that exploded was attached to a drum of petrol. The party condemned the attack as reckless and said anyone passing near the device could have been killed or wounded.
Police have given no indication as to who may have planted the bombs.
Two explosive devices were found and made safe by security forces over the weekend. One was at Belfast International Airport and the second was placed under a railway bridge in County Armagh.
Assistant Chief Constable Duncan McCausland on Sunday blamed the bombs on "misguided individuals and groups who seek to drag the country back to mayhem and misery."
Northern Ireland suffered decades of violence between pro-Irish republicans and pro-British unionists, which left about 3,000 people dead.
The violence was largely ended by the Good Friday Agreement of 1998, which set up a power-sharing mechanism and led to local government in the province rather than direct rule from London.