The Palestinian group Hamas announced on Monday that 31 tombs dating back to the first century A.D. have been unveiled by construction workers at a building site in northern Gaza.

The Roman-era tombs were discovered near the town of Beit Lahia as work began on an Egyptian-funded residential area, part of the $500 million reconstruction package Cairo pledged after the 11-day war in May between Israel and armed groups in the Gaza Strip.

Naji Sarhan, an official at Gaza's Ministry of Public Works, confirmed the find and said there is "evidence that there are other graves" at the site.

Construction work has been halted and technicians from Gaza's Ministry of Antiquities and Tourism have been sent to the site to catalog gravestones and artifacts, officials said.

One technician, who requested anonymity, said the tombs were believed to be part of a cemetery linked to a nearby Roman site in Balakhiya.

The find was the latest in Gaza, where tourism to archaeological sites is limited due to an Israeli blockade imposed since Hamas took over the strip in 2007.

Israel and Egypt, which share a border with Gaza, tightly restrict the flow of people in and out of the impoverished strip, which is home to about 2.3 million Palestinians.

Last month, Hamas reopened the remains of a fifth-century Byzantine church following a years-long restoration effort backed by foreign donors.