Russian investigators have traced the cause of last month's Proton launch failure to a damaged cable fastened to an open-air truss connecting the booster's first and second stages, the rocket's commercial marketing firm said Thursday.

The Proton was carrying a Japanese telecommunications satellite during a Sept. 5 launch from the Baikonur Cosmodrome in Kazakhstan.

The cable damage prevented commands from being routed to pyrotechnic bolts joining the Proton's first and second stages, according to an International Launch Services statement.

The pyro bolts are designed to fire to sever connections between the stages about two minutes after liftoff.

The Proton's four second stage engines ignited as planned seconds before the rocket was to shed its first stage, but the explosives did not fire to separate the two booster components, according to the results from the Russian State Commission inquiry.

The second stage engines - burning a hydrazine fuel derivative and nitrogen tetroxide oxidizer - cut off moments later as the Proton began to tumble out of control, according to Russian news reports.

U.S.-based ILS manages marketing and sales efforts for the venerable Russian booster, which has amassed 327 flights through more than four decades of service. ILS is jointly owned by Space Transport Inc. and Khrunichev, the prime contractor for the Proton rocket.

"I am very confident that the Russian State Commission was able to conclude its investigation thoroughly and in a timely manner," said Jim Bonnor, ILS vice president and chief technical officer.

Bonnor chairs the ILS Failure Review Oversight Board, which is independently reviewing the commission's findings.

The Proton is scheduled to return to flight later this month on a mission to deliver three Glonass navigation satellites into orbit for the Russian government.

But those launch plans hinge on whether Russia and Kazakhstan can quickly settle claims regarding damages inflicted by the falling rocket. Kazakh government agencies are demanding Russia pay $60 million in compensation, according to Russia's Novosti news agency.

Kazakhstan banned further Proton launches from Baikonur immediately after the accident. Russia must make damage payments and take further action to protect the environment before the ban will be lifted, according to Kazakh government officials.

Russia has leased the Baikonur launch site since the fall of the Soviet Union left the base inside Kazakhstan.

Debris from the doomed launcher crashed about 25 miles southeast of the Kazakh town of Zhezkazgan, Russian media reported.

Officials collected 119 fragments of the Proton, which was loaded with thousands of gallons of toxic propellant, according to the Novosti report.

"Having not only telemetry, but recovered hardware from the vehicle itself certainly facilitated the investigation and conclusions," Bonnor said.

No one was hurt in the accident, but a portion of the $60 million payment would go toward health checks of the local population in the next few years. Analysis of many soil samples retrieved from the crash site revealed toxicity levels were higher than allowable limits, Novosti reported.

Russia said they would conduct their own studies and develop an independent estimate of the cost of damages by December.

The disagreement is the most recent in a series of claims arguments between the two nations about rocket crashes.

Kazakh leaders initially asked Russia for payments worth more than $300 million after a smaller Dnepr rocket failed early during a launch last year. After months of negotiations, Russia finally agreed to pay Kazakhstan $1.1 million for a launch ban to be lifted.

The Dnepr successfully flew again in April, nine months after the 2006 failure that left rocket parts scattered across the Kazakh countryside. Paperwork issues contributed nearly three months to the Dnepr's idle time after the accident.

The Proton's scheduled Oct. 25 blastoff would come just seven weeks after last month's botched launch. ILS believes commercial missions for the booster could resume by mid-November.

"We appreciate the full support of our customers during this recovery period, as we act with diligence and determination through the investigation and return-to-flight activities with our partner, Khrunichev," said Frank McKenna, ILS president.

At the time of the September failure, the next three commercial missions on the Proton's manifest included two European communications satellites and an American direct-to-home broadcasting satellite.

SIRIUS 4 will provide communications services to customers in much of Eastern Europe for operator SES SIRIUS.

The Norwegian Thor 5 spacecraft will serve the Scandinavian nations, as well as other locales throughout Europe and the Middle East.

AMERICOM 14 is also scheduled for launch soon to begin a 15-year mission providing direct-to-home television broadcasts for EchoStar Communication's DISH Network service.