"Both satellites were confirmed separated, acquired and they are on orbit," Arianespace said in an updated statement after the lift-off from the Kourou Space Centre in French Guiana.
The European space workhorse blasted off at 7.20 pm (2220 GMT) carrying satellites for Luxembourg's SES and the United Arab Emirate's Yahsat in the first launch of the year for Arianespace.
Around an hour after the launch, CEO Stephane Israel announced that controllers had "lost contact" with the craft in what he described as an "anomaly".
In their updated statement the company said a tracking station in Brazil was unable to track the craft shortly after ignition of the rocket's upper stage.
"This lack of telemetry lasted throughout the rest of powered flight," the statement said. But both satellites were later "communicating with their respective control centres".
Since it was founded in 1980, Arianespace has put more than 550 satellites into orbit including for Europe's Galileo GPS system.
In September the company aborted the launch of an Ariane 5 rocket carrying two commercial satellites in the final countdown as the main engine was being ignited.
An Ariane 5 lift-off was also aborted at main engine ignition in March 2011.
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