A fire at an office building in Jakarta has killed at least 22 people as authorities continue to search for casualties.

The blaze at the seven-storey site in the Indonesian capital started on Tuesday afternoon, according to city police chief Susatyo Purnomo Condro, who said some workers were having lunch at the time.

Police believe the fire began after a battery exploded on the first floor before the flames spread upwards. A company which makes drones is based in the building.

Susatyo said most of the victims who perished were women, one of whom was pregnant, and it was likely that they had died of asphyxiation from smoke rather than burns.

Thick smoke poured from the upper floors as firefighters deployed 28 engines and about 100 personnel, with dramatic footage showing trapped employees being rescued by aerial ladders.

The fire has been extinguished and rescue teams are focusing on the upper levels of the building after conducting a sweep of the lower floors.

Susatyo said that access to the sixth floor was “particularly challenging, according to the firefighters on site”, the Jakarta Globe newspaper reports.

“We are still collecting data,” he told the Associated Press news agency. “But for now, we are focusing on identifying the victims who have been found.”

The company provides drone services for industrial clients, from aerial surveying and mapping to inspection and agriculture.