Malaysia's air force chief has denied remarks attributed to him that a missing Malaysia Airlines plane was tracked by military radar to the Strait of Malacca, far from its planned route.
Rodzali Daud said such reports in local media were untrue, but it was possible the plane had turned back.
Flight MH370 from Kuala Lumpur to Beijing went missing on Saturday, after taking off with 239 people on board.
Meanwhile, Vietnam said it was scaling back some of its search activities.
"We've decided to temporarily suspend some search and rescue activities, pending information from Malaysia," Vietnam's deputy minister of transport Pham Quy Tieu said on Wednesday.
Earlier this week, Malaysia widened the search for the missing plane amid conflicting reports on its last known position. Early search efforts focussed on waters between Malaysia and Vietnam.
On Wednesday, Gen Rodzali Daud said he "did not make any such statements", but the air force had "not ruled out the possibility of an air turn-back".
Meanwhile, AFP news agency reported that the search had been expanded into the Andaman Sea, north of the Strait of Malacca, citing Malaysian civil aviation chief Azharuddin Abdul Rahman.