SAN FRANCISCO - THE popular online social network Facebook is being sued by a woman who alleges it has profited from its members sending thousands of unauthorised text messages to mobile phone users whose numbers previously belonged to other people.

The lawsuit, filed on Monday in a San Jose federal court, highlights the confusion and frustration that can arise as Web sites extend their services to mobile handsets with phone numbers that have been reassigned, or 'recycled,' after another customer's service ended.

Lindsey Abrams, a Patriot, Indiana, mother in her mid-20s, alleges she began receiving unsolicited text messages apparently intended for an unidentified Facebook member shortly after she received a new mobile number from Verizon Communications in November 2006.

The messages included explicit language and unsettling remarks, according to Ms Abrams' civil complaint. She alleges she was charged 10 US cents (15 Singapore cents) per message and told she could not block the Facebook texting without cutting off notes she wanted to receive.

The lawsuit, which her lawyer will seek to have certified as a class action, contends other consumers with recycled phone numbers have been besieged with unsolicited Facebook text messages containing party invitations and unwanted sexual advances.

Young children have been among the recipients of the unauthorised Facebook messages, the suit alleges, creating 'frightening and dangerous' situations.

Facebook spokeswoman Brandee Barker declined to comment on the allegations, citing the Palo Alto-based company's policy not to discuss lawsuits.

The complaint against Facebook's 18-month-old mobile messaging service comes less than a week after the privately held startup reached an agreement with New York State Attorney General Andrew Cuomo to step up its policing efforts to protect minors from sexual predators and inappropriate content on its Web site.

Jay Edelson, a Chicago attorney representing Ms Abrams, said he hopes to force Facebook to take steps so its roughly 47 million members won't be able to send text messages to recycled phone numbers.

'There are things that Facebook could be doing to prevent this from happening,' Mr Edelson said. 'Hopefully, this suit will give them the incentive to stop it.' The lawsuit also seeks unspecified damages. -- AP