A fire and explosion on a crude palm oil tanker at a shipyard on Indonesia’s Batam Island killed at least 10 people and injured 21 others on Wednesday.

The blaze erupted in the ship’s gas tank while repair workers were still on board, followed by a powerful explosion that caused panic.

Four of the injured are in critical condition, and relatives gathered at hospitals seeking information about loved ones, the AP has reported.

The tanker, built in 2009, had a similar accident in June that killed four and injured five, reportedly caused by welding sparks and smoke inhalation.

Authorities are investigating the cause and possible negligence by the shipyard operator, PT ALS.