* Death toll climbs to 236 as victim succumbs to injuries
* Doctors say more could develop respiratory problems (Recasts with extended detention, preliminary testimony)
SAO PAULO, Feb 1 (Reuters) - A judge in southern Brazil ordered 30 more days of detention on Friday for the owners of a nightclub and band members involved in a fire that killed 236 in the college town of Santa Maria last weekend.
The order came after a 20-year-old woman succumbed to her injuries late Thursday, pushing up the death toll from the country's second most deadly fire ever.
Civil defense authorities in Rio Grande do Sul, the state where Santa Maria is located, said the victim suffered a heart attack while struggling with injuries that included burns on more than half her body.
An additional 126 people remain hospitalized after the fire, which was caused by an outdoor flare set off by a musician performing at the Kiss nightclub, investigators said. The flare ignited overhead soundproofing, a synthetic foam that burned and within minutes spread toxic fumes throughout the venue.
Most of the victims died after inhaling the fumes, investigators concluded on Thursday.
Many of those in nearby hospitals, more than half of whom are on respirators, have developed scorched airways and inflamed lungs from the poisonous vapors. Authorities fear more survivors could be sickened by the fumes, noting that it may take a week for symptoms to appear.
On Friday, a judge extended the detention of two owners of the club and two band members for 30 more days as police look into safety violations that led to the disaster early on Sunday.
The judge considered preliminary testimony from an employee faulting club owners for faulty extinguishers and carelessness about overcrowding. The owner of a fireworks store testified that he had warned the band's producer that the flare was banned for indoor use.
Lawyers for the club owners and band members have maintained their innocence. Police have not yet charged any of the four detainees, but said at minimum they are likely to face manslaughter charges.
Prosecutors are also investigating city and fire officials to determine if they were negligent in allowing the club to remain open despite safety violations including broken exit signs and blocked access to the club's only exit.
The factors led to a stampede that crushed some of the victims and kept others from fleeing the flames and toxic smoke. (Reporting by Daniela Ades and Eduardo Simoes; Writing by Paulo Prada and Brad Haynes; Editing by Vicki Allen)