Washington, May 29 (IANS/EFE) The number of deaths caused by last weekend's tornado in Joplin, Missouri, has risen to 139, authorities said.

Almost a week since the disaster and on the eve of a visit by President Barack Obama to the area, officials told a press conference that the number of dead could continue to rise, according to the daily The Joplin Globe.

More than 400 volunteers and emergency management experts continued to comb the immense tracts of rubble searching for the missing, many of whom could not get in touch with their families during the tornado, the deadliest in the area since 1950.

The list of missing people updated Saturday by Missouri's Department of Public Safety dropped from 156 to 96 on a list that changes every time another body is found or a family calls in to say they have found a loved one alive.

Joplin Mayor Mark Rohr said Friday that the scores of confirmed fatalities could have a "significant overlap" with the list of the missing.

Nonetheless, he said it will take time to find out if that is the case, given that many of the dead have not yet been identified and the authorities still hope to find more survivors.

"We're going to be in a search and rescue mode until we remove the last piece of debris," Rohr said.

Meanwhile, state authorities announced Saturday that Joplin residents can now use tap water for drinking or brushing their teeth, and no longer have to boil it as they had to do all week.

The tornado, which left a path of devastation almost 10 km long and almost a km wide when it struck the city last Sunday, damaged more than 8,000 structures, left 900 people injured and caused millions of dollars in losses.

The National Weather Service classified it in the EF-5 category, the highest on its scale, with winds of more than 320 km an hour.

Though the most devastating tornado was the one in Joplin, storms and tornadoes associated with the same weather system left 13 dead this week in Kansas, Arkansas and Oklahoma.