1. A computer program product comprising a non-transitory computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to perform a method comprising: generating a time-marked word list of an automatic speech recognition system, wherein generating the time-marked word list comprises converting an indexing structure into an output, and wherein the time-marked word list comprises the output; generating an index from the time-marked word list, wherein generating the index comprises creating a word loop weighted finite state transducer for each utterance, i, of a plurality of utterances; receiving a plurality of keyword queries; and searching the index for a plurality of keyword hits; wherein the word loop weighted finite state transducer for each utterance, i, of the plurality of utterances, includes S i as a start node, E i as an end node, without a start node or an end node between S i and E i and a plurality of arcs connected between an S i to E i pair for each utterance, the plurality of arcs corresponding to each word label, start and end time, and posterior probability in the time-marked word list.