The BBC's Tom Carver says it will be a long time before the women of Mexico receive the protection they need

It is thought that nearly 120 women have been killed so far and the manner of their deaths suggests it is the work of one man.

Evidence suggests work of an organised serial killer

The US criminal psychologist, Robert Ressler, says he believes the murderer could be an American citizen who crosses the border to commit his crimes.

Mexican police in the border town, Jaurez, have arrested one man, but the murders have continued at the rate of about one a fortnight.

Lured by work

Many women are drawn to the town by prospects of employment at foreign-owned factories - for which they are paid an average of $5 a day.

Victim's sister: still traumatised

Ahalia was one woman who worked in these factories. But on March 13 she never returned.

A month later her body was found stuffed into a storm drain. Like many of the other female victims, she had been raped and strangled.

She left behind a five-year-old daughter.

But despite the large number of victims, the women's families are usually poor and have little influence over the authorities investigating the crime.

A BBC correspondent says the police are anxious to play down the possibility of a serial-killer and often seem indifferent to the victims.

The Chief Prosecutor, Jorge Lopez Molinar, said: "Some of the cases have already been solved and have no relation to the others."

Mr Ressler studies the evidence

But despite their apparent confidence, Mexican police have asked for help from Mr Ressler.

He believes the murderer could be an American.