Eight people have breached the perimeter at Denver International Airport in the last decade, most of them by climbing the fence surrounding the 53-square-mile property, according to an Associated Press investigation.

The AP found there have been at least 268 perimeter security breaches at 31 major U.S. airports from January 2004 through January 2015. Incidents ranged from fence jumpers taking shortcuts and intoxicated drivers crashing through barriers to mentally ill intruders looking to hop flights. None was terrorism-related.

Airports say breaches are relatively rare. Security measures typically include fences, cameras and patrols, but there are gaps. Not all of the miles of fences are routinely patrolled or covered by video surveillance.

DIA spokeswoman Laura Coale noted that the airport is twice the size of Manhattan.

“We believe many folks do not realize they are even on airport property — it looks like farmland and a breach may be miles and miles away from a runway or the terminal,'' she wrote in an email.

The incidents DIA reported based on AP's inquiry were:

• Nov. 27, 2014: An intoxicated 28-year-old man drove through a perimeter gate.

• July 16, 2011: A man who said he was trying to get home climbed a security fence after failing to get off at the right bus stop.

• Feb. 10, 2010: A man said he walked to the airport and climbed the security fence to get to a terminal.

• April 23, 2009: A man who climbed the security fence said he was walking to work nearby.

• Aug. 27, 2008: The impaired driver of a truck towing a horse trailer drove through a gate.

• Oct. 27, 2006: A driver whose vehicle broke down climbed a security fence to seek assistance.

• Oct. 21, 2006: A 54-year-old man said he hitchhiked to the airport and was dropped off on the wrong side of the airfield, so he jumped the security fence to get where he wanted to go.

• March 15, 2004: A 41-year-old man climbed over a security fence. He told authorities he was walking in the desert after riding a bus from California to Denver.