Police, ambulance and six fire appliances attended the fire, believed to have involved two mattresses in one of the cells.
The fire was out on arrival and half the fire crews left the prison.
A Department of Fire and Emergency Services (DFES) spokeswoman said the blaze caused about $4000 damage.
She said DFES would not investigate the cause of the fire because the matter was a decision for prison management.
A Department of Corrective Services spokesman said an investigation to determine the cause was being held.
More information about whether the fire was accidental or deliberately lit was not available.
The spokesman said prisoners and prison officers were permitted to light up in designated areas at the prison, but not inside cells.
“These areas are to be at least 5m from a doorway or window and 10m from any building ventilation equipment, including airconditioning units,” he said.
The WA Prison Officers Union (WAPOU) last year called on Corrective Services Minister Joe Francis to reconsider his refusal to impose a total smoking ban in prisons.
Mr Francis said banning smoking in WA prisons was “a bridge too far”.
After speaking with inmates and prison officers, he said there was division over a ban.
Mr Francis also raised concerns over the benefits of a complete ban outweighing the potential for a negative impact on security and tension in prisons.
WAPOU secretary John Welch said smoking inside prison buildings became unlawful about seven years ago.
But because it is allowed in outdoor areas, prisoners have cigarettes in their possession.
He said that made it ‘very difficult’ to prevent prisoners from smoking in cells and in non-designated areas.
“We do not want prison officers having to go into cells where someone has been smoking,” he said.
WorkSafe confirmed it had investigated complaints about prisoners smoking outside designated areas last year.
Mr Welch said passive smoking was a health and safety issue recognised by the government in other areas.
Total smoking bans in prisons are in place in most other Australian states and territories.
The union chief also called for the government to act over chronic overcrowding at the women’s prison. Bandyup, which is the most overcrowded prison in the state according to the Inspector of Custodial Services.
The Government had hoped a $20 million women’s remand centre at male-only Hakea Prison would be up and running by mid-year.
Construction is due to start this month, but the 256-bed facility will not be ready until the end of the year.
A Department of Corrective Services spokesman said Bandyup would have another 115 beds, meeting one of 25 recommendations from the Office of the Inspector of Custodial Services in 2014.
He said as of December 18 last year, Bandyup had 304 prisoners and the total capacity was 394 inmates.