The agency said it was checking reports the death toll was as high as 78.
Redmond said the the higher death toll came from a construction company helping to bury the dead migrants along the coastline.
He said: "We know it is at least 30 and possibly as high as 78."
It was the second mass drowning of African migrants this month in the Gulf of Aden.
Fifteen Ethiopian and Somali migrants died after traffickers forced hundreds of passengers to disembark from two boats far from the Yemeni shore in early February.
Smugglers, usually Somali, often drop the migrants in deep waters as the Yemeni coastguard has increased patrols near shore, according to the UNHCR.
About 27,000 people made the perilous journey from Somalia last year, fleeing fighting in the volatile Horn of Africa nation between the Ethiopian army and the Islamic courts movement.