Updated

No arrests have been made in what police say was an arson at a Quaker meeting house under construction with nonunion labor, Philadelphia authorities told FoxNews.com.

Vandals cut anchor bolts and used torches on structural columns in the future meeting house's community room, authorities said. They also set fire to a crane on the property. Police believe the Quaker building was targeted because it is being built with nonunion labor.

"I absolutely think it is a union issue," Philadelphia Police Lt. George McClay told the Philadelphia Inquirer.

The fire broke out sometime overnight after the Dec. 20 shift ended at 20 E. Mermaid Lane, according to police. The incident drew the Philadelphia Fire Department, a bomb squad and representatives from the Police Civil Affairs Unit. The site is the future worship space for the Chestnut Hill Friends Meeting House, said Rob Reeves, whose company is the general contractor for the project. He had little doubt who the culprits were.

"I have a strong suspicion it's union people," Reeves, who estimated the damage at $500,000, told Newsworks. "The issue here is violence and bullying."

Area residents and members of the Quaker community were shocked that pacifist group could be targeted for violence. Chestnut Hill Friends broke ground on the $ 6.2 million project May 15, after raising $3 million for the project, which also won grants from the National Endowment for the Arts and the William Penn Foundation.