BEIJING — Investigators in China said “multiple human errors” caused a transport truck laden with Lunar New Year fireworks to explode, state media reported Saturday.

“Those suspected of being involved in the accident have been taken into police custody,” the investigation team said, according to Xinhua news agency, of the explosion that killed 10 and demolished part of an elevated expressway on Friday.

Earlier Saturday, state media reported that at least 11 people died when the 80-meter (262.5-foot) section of a four-lane bridge collapsed near Sanmenxia in Henan province, sending at least 25 vehicles plunging 30 meters (98.5 feet).

The report did not identify or say how many suspects were detained, although Xinhua earlier reported that four people were held after documents were found saying the truck was transporting only general merchandise.

The investigators told Xinhua that an illegal fireworks manufacturer from northwestern China had hired an unqualified contractor to transport wrongly packaged products in the wrong kind of vehicle without checking the contractor’s drivers, licenses or qualifications.

“Relevant people from both the manufacturer and the transport enterprise are suspected of law and regulation violations,” Xinhua quoted the team as saying.

The team also confirmed the blast as the cause of the bridge collapse, even as skeptical Internet users cast doubt on the quality of the bridge, which opened in 2001, passing a safety inspection in 2011.

• Associated Press