Complex sentence: After a month had passed with little progress in the case, police continued to focus their investigation upon Echols, interrogating him more frequently than any other person; however, they claimed he was not regarded as a direct suspect but a source of information.
Split into simpler sentences: After a month had passed with little progress in the case, police continued to focus their investigation upon Echols, interrogating him more frequently than any other person. Nonetheless, they claimed he was not regarded as a direct suspect but a source of information.