A large vegetation fire began burning Thursday afternoon on a hilltop near the U.S.-Mexico border.

Smoke from the so-called Border 2 Fire was visible for miles. It’s not yet known what, if any, resources, have been assigned to the blaze, though a fixed-wing aircraft was seen making a water drop on what is obviously a fast-growing fire. Later in the day, multiple aircraft were assigned to fight the flames, according to Cal Fire.

Flames from the fire could be seen racing up a hillside on Otay Mountain, near the Otay Mountain Truck Trail.

At a little before 2:30 p.m., Cal Fire San Diego tweeted out that the border fire had already burned 20 acres and had a “dangerous rate of spread.” This fire, said officials, who had ordered additional resources to battle it, had the potential to grow to 500 acres. Ninety minutes later, the fire had spread to 140 acres and was at 0% containment.

During the afternoon, the fire crested Otay and “impacted [a] communications tower at the top of the mountain,” according to Cal Fire.

A second fire began burning almost simultaneously in La Jolla near Gilman Drive, not far from the campus of the UC San Diego. That fire, which was not nearly as large — an original estimate was a single acre — prompted evacutions in the heavily populated area.

The fires come in the wake of a series of blazes this week, including ones in Mission Valley near the Fashion Valley Mall and in Rancho Bernardo, as well as a second small one in Mission Valley on Thursday morning started in a homeless encampment.

NBC 7

A fire began burning in a remote area near the U.S.-Mexico border on Thursday.

Most concerning for firefighters and residents, though, is the fact that Thursday’s forecast is for the strongest winds of a week of Santa Ana’s.

Check back here for updates on this breaking news story — Ed.