More and more the Golden Gate Bridge is being buzzed by camera-carrying flying drones, and security-conscious span officials are none too happy about it.

Several times a month bridge officials notice remote-controlled drones flying around the span.

“The increased presence of these unmanned aircraft is a major threat, and is of significant concern to those charged with the security of the Golden Gate Bridge,” read part of a letter sent last month to Sen. Dianne Feinstein, who is looking into drone issues.

One of the drones even crashed into the span’s roadway recently, said Denis Mulligan, the bridge district general manager, raising the issue of traffic, pedestrian and bicycle safety.

“It’s a big issue, and there are no restrictions on the drones,” Mulligan said.

The drones have been seen flying behind security fences and past sensors where the bridge prohibits photography for security reasons. Designated by the U.S. Department of Homeland Security as “critical infrastructure,” the bridge district has received roughly $15 million in state and federal grants for security improvements since the 9/11 attacks for both the span and its transit systems.

But some of the security measures are being bypassed by drones — and it’s not illegal. Presently there are no laws on the books to cite drone operators if they are identified — which is difficult to do as they fly the craft remotely.

“If you find the person who flew the drone in areas where they are not supposed to, you can’t cite them for trespassing,” Mulligan said. “But if you climb over a fence and take pictures we can cite you. There should be some mechanism to place restrictions on airspace for security reasons.”

The Federal Aviation Administration has proposed a framework of regulations for commercial drone operators including limiting flights to daylight and requiring visual line-of-sight operations. It also addresses height restrictions, operator certification, optional use of a visual observer, aircraft registration and marking and operational limits.

The bridge district has written the agency, saying that while it supports the proposals, it should include non-commercial users because of potential security and safety issues.

“There is some dramatic drone footage out there,” bridge board member Brian Sobel said of video taken by drones. “It’s HD, it’s clear as a bell, it’s pretty remarkable, and it shows up on all sorts of websites.”

That’s not to say the bridge district is completely anti-drone.

“Drone technology is phenomenal; we see it as a great tool for bridge inspection for areas that are hard to get to,” Mulligan said.

“But there needs to be some rules.”