TAIPEI (Taiwan News) — The fire department said it expects to complete its report on last month’s deadly Taichung mall explosion in around three weeks, as councilors criticized the investigation's pace on Wednesday.

DPP, KMT and independent Taichung councilors raised concerns about the fire department’s investigation of the Shin Kong Mitsukoshi explosion at a city government meeting, per Now News. Authorities suspect a gas leak caused the blast that killed four and injured 39.

Councilors Wu Pei-yun (吳佩芸) and Huang Shou-ta (黃守達) asked the fire department if it would submit a report on the explosion within the required 30-day deadline. They noted that it will be one month since the explosion on Thursday.

Fire Department Chief Sun Fu-yu (孫福佑) responded by saying two explosion victims cannot be questioned as they remain in intensive care. He said a gas leak is still the suspected cause, though new evidence has been found recently.

Sun said the fire department is investigating the new evidence, but he could not share information about it publicly. He said due to the incident's seriousness, he has extended the deadline for a report to the end of the month.

Also on Wednesday, the Taichung District Prosecutors Office told CNA that it is continuing investigations to determine responsibility for the explosion. The office said it has questioned 33 people since the incident, including 11 construction workers this week.

It said prosecutors had questioned some witnesses more than once. Prosecutors have worked with the fire department and police on multiple on-site investigations, it said.

The Shin Kong Mistukoshi Department store has remained closed since the explosion. The city government said work to secure the site, including a net to cover its exterior, must be completed by the end of the month.