Firefighters are trying to determine the cause of a two-alarm fire that injured a 54-year-old man and left an apartment uninhabitable on Vineyard Boulevard, firefighters said.

Honolulu Fire Department spokesman Kendall Ching said the fire started at 404 N. Vineyard Blvd. at about 2 p.m., and arriving units saw smoke coming from a ground-floor unit.

About 30 firefighters extinguished the fire in 19 minutes, but not before it caused extensive damage to the two-bedroom apartment, Ching said. Firefighters called the Red Cross to assist three residents.

One man was taken out of the unit and transferred to paramedics, Ching said. The man was taken to the hospital in serious condition, an Emergency Medical Services report said.

Firefighters estimated the fire caused $140,000 in damage.

Suspect arrested in assaults in Waipahu

A 19-year-old man was arrested after he assaulted a man and a woman in Waipahu, police said.

The suspect confronted a 20-year-old man at about 11:15 p.m. Saturday and assaulted him, causing him to lose consciousness, police said.

When a 21-year-old woman tried to help the victim, the suspect also assaulted her, police said.

The Waipahu man was arrested near Zippy’s Waipahu at 11:45 p.m. on suspicion of felony assault and misdemeanor assault.