“There is no clear trace of explosives at the site. Forensic tests are still ongoing,” Central Police Forensic Science Division’s chief Pol Maj-General Tawatchai Mekprasertsuk said Tuesday.

On Monday night, a big bang was heard in front of the theatre and there were reports that two women were slightly injured.

“When we arrived at the scene, we found broken PVC pipes. These pipes were used to hold up an advertisement board,” Tawatchai said. “We have collected evidence at the scene for examination.”

He said substances gathered at the scene could provide clues as to whether the sound resulted from a bomb blast.

“The results should come out within a day or two,” Tawatchai said.

Meanwhile, Deputy Bangkok Governor Pol Lt-General Amnuay Nimmanon said the site was cordoned off to facilitate the work of police and officials.

“We have also given footage from security cameras in the area to police and the Joint Administration of Security and Order Maintaining for the Grand Palace,” he said.

The joint administration has been active in the area for seven months to ensure the safety of people as many have visited the area to pay respects to the late monarch, HM King Bhumibol Adulyadej.