TAIPEI (Taiwan News) — Taichung police questioned witnesses overnight on Thursday as the number of injured following a fatal gas explosion rose to 30.

Police sent 12 people, including construction and department store workers, for questioning after a possible gas explosion at Shin Kong Mitsukoshi department store left four dead, per CNA. Police said 20 others, including Shin Chung Natural Gas employees, were asked to appear and make statements.

Prosecutors said work is ongoing to secure the Shin Kong Mitsukoshi site and determine what led to the explosion. They said a subsequent investigation would find who is responsible.

After the incident, Shin Chung Natural Gas said no gas pipeline issues could have caused the explosion. The company said that after Shin Kong Mitsukoshi signed off on renovations, it sealed off pipelines and removed old meters on Monday.

Meanwhile, Taichung City Government said in a statement on Thursday afternoon that the number of people injured had risen to 30. This is in addition to the four people confirmed dead earlier in the day.

Taichung Mayor Lu Shiow-yen (盧秀燕) said she ordered the Shin Kong Mitsukoshi branch to suspend operations until investigations are complete. She said the urban development, labor, and fire bureaus are all involved in the investigation.

Lu said city government departments may impose up to NT$300,000 (US$9,164) fines for breaking the Building Act, and the fire department may impose up to NT$600,000 fines for each regulatory violation found. 

Lu said the Mainland Affairs Council would assist the seven-person Macao family affected by the blast. Two of the family members were killed, and a 2-year-old is reported in critical condition.