By Nick Miles BBC News, Washington

Many of Katrina's victims who fled to Houston still have not left

One in five of the murders in the city over the last year involved an evacuee as either the suspect or victim.

There was also a marked increase in the overall number of killings.

Almost a year since the hurricane hit New Orleans, hundreds of thousands of people are still living in temporary housing across the United States.

The figures are striking. Murder rates in Houston are up by almost 20% in a year.

A disproportionate number of them involve people who fled Hurricane Katrina.

Houston received the bulk of those rescued after the flooding in New Orleans - 150,000 of them.

The majority came from New Orleans' most disadvantaged areas, arriving in Houston with few possessions and little money.

Many of them have been living in areas where unemployment levels and crime rates are high.

Over the last year there were 232 murders in the city, and one in five involved a Katrina evacuee.

One explanation for that could be that as displaced gangs compete for space in a new environment there is likely to be an upsurge in violence.