BECKER, Minn. (AP) — Officials are monitoring the air quality in Becker where a fire at a metal recycling plantcontinues to burn.

Firefighters continued to fight the stubborn blaze Wednesday after working all day and through the night Tuesday at Northern Metal Recycling plant.

The fire still had a number of hot spots and was not fully under control as of early Wednesday afternoon.

In a Facebook update Wednesday evening, the Becker Police Department said fire investigators believe the fire could last several more days. Residents are not being asked to evacuate but are being asked to stay away from the immediate area of the fire.

Becker Police Chief Brent Baloun says the cause of the fire remains unknown. Prevailing winds have been blowing smoke away from Becker.

“We’ve been fortunate with the wind,” Baloun said.

But residents in Big Lake, 9 miles (14 kilometers) southeast of Becker, caught most of the drift Wednesday. Big Lake Police Chief Joel Scharf says the smell of burning plastic and smoke wafting through town raised health concerns from residents.

Firefighter Toni Knutson says the fire is burning under a huge pile of cars. She says cranes are being used to remove the vehicles from the pile one-by-one as firefighters spray water on the fire.

Knutson says dozens of firefighters are on the scene, with aid coming from as far as two hours away.

The city requested help from the National Guard, the state Pollution Control Agency and Health Department.

The Star Tribune reports police have told residents with respiratory problems who live near the plant to stay inside or in well-ventilated areas. As of noon Wednesday, the Health Department had no reports about any unusual, imminent threats.

A passerby first spotted the fire about 2:30 a.m. Tuesday.

Northern Metals moved its shredding operation from Minneapolis to Becker last year after the Pollution Control Agency ordered it shut down because of high levels of air pollution and inaccurately recorded pollution readings.

Becker, with a population of about 4,500, is about 48 miles (77 kilometers) northwest of Minneapolis.