* Number of fires falls to 56
* Prime minister pledges to help affected residents
* No indication yet when Rainbow oil pipeline will restart
By Todd Korol
SLAVE LAKE, Alberta, May 20 (Reuters) - Damp weather helped crews douse the number of wildfires raging across northern Alberta on Friday as Canadian Prime Minister Stephen Harper toured the town of Slave Lake, where hundreds of homes, businesses and public buildings went up in flames.
A big volume of oil production in the region remained shut off due to the closing of a major pipeline as 56 fires continued to burn across the north of Canada's biggest energy producing province. Ten of them were out of control.
That is down from more than 100 fires burning at the start of the week. So far, 2,638 square km (1,019 square miles) have burned, an area about the size of Luxembourg.
Slave Lake's more than 7,000 residents remained evacuated and some structures still smoldered five days after two blazes, whipped by high winds, converged on the town, a center for the oil and gas and forestry industries.
After touring the region by miliary helicopter, Harper met with ash- and soot-covered firefighters and emergency personnel at their command center in Slave Lake and thanked them for their efforts.
"You have to look at the bright side -- it's a miracle that there was no loss of life," Harper said.
Factbox on affected energy operations: [ID:nN17146041]
Link to map of fire locations: here
In a statement, he said his government would work closely with the other levels of government to help residents through the tragedy. The amount of federal financial assistance is not yet known
The Alberta government has pledged an initial C$52 million ($53.6 million) to help with the immediate needs of evacuees of Slave Lake and the surrounding region.
The oil industry continued to be hit as more than 140,000 barrels a day of production from companies such as Cenovus Energy Inc (CVE.TO), Penn West Exploration PWT.TO and Canadian Natural Resources Ltd (CNQ.TO) was unable to flow.
Much of that was because Plains All American Pipeline LP's (PAA.N) Rainbow crude line was shut down due to fire danger, and some was due to fires drawing close to oil fields.
A spokeswoman for Plains said there was no indication yet when the southern leg of the Rainbow pipeline would be able to restart. It serves the Pelican Lake, Alberta, oil fields.
Depending on conditions, crews are expected to return on Tuesday to a site on the northern section of the line to finish cleaning up an oil spill that occurred in late April.
So far, the outages have had minimal impact on Canadian crude markets, as the volume is a small fraction of Canada's 2.8 million barrels of daily production.
However, analysts have said fires will have a larger influence on the market if they prevent production for a much longer period or if they threaten oil sands production farther to the east.
$1=$0.97 Canadian Writing by Jeffrey Jones; editing by Peter Galloway