Two Spanish-language radio stations tumbled in the ratings last month in the key morning-drive time period, according to numbers from Nielsen Audio.
Radio stations have been anticipating the May report, which had been delayed for more than a week after Nielsen acknowledged problems with its sample audience in Los Angeles. The ratings firm removed two problematic households from its sample and the new numbers reflected those changes.
The drops for KSCA-FM (101.9) and KXOS-FM (93.9) were significant.
KXOS' morning show featuring Ricardo "El Mandril" Sanchez fell to No. 14 in May, after it had surged to the No. 4 slot during the April measurement period.
The station's share of weekday 6-10 a.m. radio listening was cut by about 37%. KXOS' listening share fell to 2.7% last month from 4.3% in April.
KSCA's share slid to 4.1% from 4.6%.
Univision said Monday that it fired a programming executive at KSCA for scheming to pump up the station's numbers. The executive, not named by the company, had access to measurement devices that Nielsen uses to determine audience sizes.
Nielsen said it has launched "an immediate and aggressive review" of the breach and said the problems with its ratings could date back at least a year.
Nielsen's May numbers were supposed to be sent out last week, but the company said it needed to delay the release because it was investigating the problems. The company also said it would revise its April numbers.
Those revisions are set to come out Thursday.
CBS' classic-hits station KRTH-FM (101.1) scored the top spot in the morning drive after finishing in sixth place in April.
In term of overall audience share Monday through Sunday, the top three were KIIS-FM (102.7), KRTH and KBIG-FM (104.3).