Noting that UP was ruled by BJP government, Shah, while addressing a poll rally here, said, ''I want to assure the people of Kerala that the culprits behind this incident will be brought to justice at the earliest''.
The issue was raised before Shah by party's Kanjirappally assembly candidate for April 6 polls, K J Alphonse, who is his former ministerial colleague in the union cabinet.
Two nuns and two postulants were taken off an express train and detained for questioning by railway police in UP's Jhansi on March 19.
The Kerala Catholic Bishops Council (KCBC) had expressed concern over the matter.
The Congress and BJP took up the matter with Prime Minister Narendra Modi and Uttar Pradesh Chief Minister Yogi Adityanath, respectively.
Officials in Jhansi said the nuns were detained after local Bajrang Dal activists complained that two of the women were allegedly being taken forcibly for religious conversion.
The police said there was no basis in the complaint and all four women later took the next train to their destination in Odisha.
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