UPDATE: Police, fire crews and ambulances were called to a fire sparked by a suspected drug lab explosion in South Lake last night.
About 50 people from nearby houses and businesses rushed to the scene after loud bangs came from the Glenbawn Drive unit about 8.30pm.
One witness described the explosion as “like a fireworks display” and said sparks rose as high as power poles.
“I was walking with my nieces and nephew when there was an explosion and we all dropped to the ground,” he said.
“We called triple-0 because we thought there might be people inside. It was like lava coming out of a volcano.”
The fire gutted one unit in a block of three and took 18 firefighters three hours to put out.
Success Fire station incident control officer Shaun Farrell said the damage bill was estimated at $200,000.
A neighbour, Michelle Colvin, said she rushed inside the unit to rescue a woman, aged in her 60s.
"The ceiling was starting to come down and two boys ran from the house,” she said.
Police said this afternoon that two men were seen running from the house after the incident.
"We believe that they are connected to the property," a police spokeswoman said.
"One male is in custody helping with inquiries.
"There is no confirmation that he was one of the two running from the house."
Police said they had spoken to the female tenant of the property.
"It is yet to be determined whether she was home at the time," the spokeswoman said.
Earlier yesterday, police were called to Cleaver Street in West Perth after reports of possible toxic chemicals inside a unit.
A police spokeswoman said officers suspected drugs were being manufactured inside the house.
Neighbouring units were evacuated about 5pm.
Anyone with information is asked to call Crime Stoppers on 1800 333 000.