■ The fire that forced the shutdown of I-5 in Northern California grew.

Blaze forced shutdown of 14-mile stretch of I-5

The massive Delta Fire that forced the shutdown of a 14-mile stretch of Interstate 5 in Northern California this past week continues to grow, and the major north-south artery is expected to remain closed until at least Sunday, authorities said.

By the end of the day Friday the wildfire had burned 31,325 acres, fire officials said. On Saturday, it had jumped to 36,970 acres.

There is zero percent containment.

More than 1,800 firefighters are battling the blaze, said Capt. Brandon Vaccaro, a media spokesman. He said more resources have been requested by Cal Fire.

Two single-family residences have been destroyed by the fire, as well as two combination residential and commercial buildings, Vaccaro said. Mandatory evacuations were issued in Shasta County and Trinity County, and evacuation warnings have been given to the community of Dunsmuir.

Interstate 5 is closed from about 10 miles north of Redding to 3.6 miles south of Mount Shasta, according to Caltrans.

Vaccaro said Caltrans, the California Highway Patrol and other management organizations have been meeting daily to determine when it will be safe to open the freeway.

The current closure is scheduled to remain in effect until Sunday, but it is possible that it will stretch on beyond that, Vaccaro said. He added that flames continue to burn very close to the freeway.

“Opening the freeway is our top priority, but it needs to be safe to do so,” he said.

The Delta Fire started on Wednesday around 1 p.m. Investigators are still not certain what sparked it, but they say it was definitely human caused.

From the very start the fire’s behavior has been extreme. Motorists trapped on the freeway described towering flames up to 300 feet high.

So far, there have been no fatalities.

Weather conditions appeared to be more favorable to firefighters on Saturday than they had been earlier in the week, Vaccaro said.

Daytime temperatures were lower and the humidity was a bit higher. Vaccaro said the humidity overnight was expected to be high enough to form dew.

This should result in less extreme fire behavior and allow fire crews to make more headway, he said.

The Associated Press Lanes are closed on northbound Interstate 5 with the Delta Fire burning in the background Friday near Lakehead, Calif.