SAN DIEGO -- Local construction companies are beefing up security at their sites, following last week's arson fires at two new home developments, 10News reported.

Slideshow

See Images Of Carmel Valley Arson Attack See Images Of Flames From Previous ELF Arson

A local security system provider says a combination of cameras, fences, motion detectors and guards is best.

The Metro Arson Strike Team says people living in the area can also provide a certain degree of security.

"What is suspicious activity is difficult to get your arms around because it may be normal in one neighborhood and out of the ordinary in another and to answer that, know your neighborhood, know your neighbors," Capt. Jeff Carle said.

Banners left at Friday's fires proclaim the radical group, Earth Liberation Front, was responsible for the attacks, however, no positive connection has been made.