A person was arrested on suspicion of arson Tuesday as a massive fire tore through a warehouse containing paper products in Ontario, authorities said.

Flames that firefighters initially believed would be contained by sprinklers instead raced throughout the 1.2 million-square-foot Kimberly-Clark building near Merrill and Hellman avenues on the east end of Ontario.

“Unfortunately, the fire grew extremely quickly to where our crews needed to make what we call an operational retreat and evacuate,” Ontario Fire Department Deputy Chief Mike Weddell said.

The person who was arrested was initially reported missing, Weddell said. The suspect’s name was not immediately announced.

Authorities have not said how they believe the fire started.

The Ontario Fire Department was alerted around 12:30 a.m. and soon fielded 911 calls, Weddell said. Firefighters arrived to find light smoke showing and a small fire.

As the blaze grew, some 140 firefighters from numerous agencies were called to fight it.

The fire was contained by 7:46 a.m., the Ontario Fire Department said.

All employees evacuated safely, and no injuries were reported, Weddell said.

“We are aware of the fire at our distribution center,” a Kimberly-Clark spokesperson said in a written statement. “Safety is our top priority, and we can confirm there are no reported injuries. The facility is operated by a third-party partner, and we are working closely with them and local authorities.”

The South Coast Air Quality Management District issued a smoke advisory that was to remain in effect into the night. Smoke from smoldering plumes was expected to drift into adjacent neighborhoods, causing the index to become what is called “Unhealthy for Sensitive Groups” in some areas.

Ash was likely to fall east of the fire, into Ontario Ranch and Eastvale, the advisory said, with children and seniors urged to stay indoors because of poor air quality.

The smoke did not affect flights at Ontario International Airport, but vehicle traffic was impacted, airport spokesman Steve Lambert said.