Earlier the recruitment used to be through UPSC Engineering Services Exam for Engineers but now after 2 years halt it's through UPSC Civil Services Exam from 2022; an all India written test followed by interview for selected candidates.
ˈɜːlɪɚ ðə ɹᵻkɹˈuːtmənt jˈuːzd təbi θɹuː ˈʌpsk ˌɛndʒɪnˈɪɹɪŋ sˈɜːvɪsᵻz ɛɡzˈæm fɔːɹ ˌɛndʒɪnˈɪɹz bˌʌt nˈaʊ ˈæftɚ tˈuː jˈɪɹz hˈɔlt ɪts θɹuː ˈʌpsk sˈɪvəl sˈɜːvɪsᵻz ɛɡzˈæm fɹʌm tˈuː θˈaʊzənd twˈɛnti tˈuː; ɐn ˈɔːl ˈɪndiɚ ɹˈɪʔn̩ tˈɛst fˈɑːloʊd baɪ ˈɪntɚvjˌuː fɔːɹ sᵻlˈɛktᵻd kˈændᵻdˌeɪts.