Investigators are saying a laboratory explosion at the University of Hawaii that resulted in a researcher losing her arm was likely caused by an electrostatic charge.

The University of California Center for Laboratory Safety, which handled the investigation, released its results Friday.

Investigators say it was challenging to determine the cause of the detonation because they weren't able to inspect the accident scene until 13 days later. They also weren't able to interview the researcher so they had to rely on a fire department report.

They say a digital pressure gauge was the origin of the electrical current that caused the detonation. They also say the researcher and some equipment in the lab were not properly grounded.