Capitol Hill authorities issued an advisory to members of Congress and their staffers on Friday, warning them to stay alert as violent attacks against lawmakers have increased around Washington, D.C., in recent months.

The Senate Sergeant-at-Arms reportedly sent a bulletin to Senate chiefs of staff, administrative managers, chief clerks, and staff directors suggesting tips to reduce the risk of becoming a victim of carjackings, armed robberies, or other criminal activity around the nation’s capital.

“Local authorities note an increase in carjacking incidents in and around Capitol Hill and the District of Columbia,” the bulletin reportedly said, according to Fox News.