The preposition laut governs either the dative or genitive case. Usage with dative is more common, and has been since 1900 or so:
* laut einem Bericht (also: eines Berichts) — according to a report.
The dative case is always used for plural nouns not preceded by an article, determiner, or adjective:
* laut Berichten (not: Berichte) — according to reports.
An isolated noun of the strong declension remains uninflected in the singular:
* laut Bericht (not: Berichts) — according to the report.