We present ongoing work on the Semantic Information Retrieval Engine (SIREn), an “entity retrieval system” specifically designed to meet the requirements of indexing and searching a large amount of semi-structured data, e.g. the entire Web of Data. SIREn supports efficient full text search with semi-structural queries and exhibits a concise index, constant time updates and inherits Information Retrieval features such as top-k queries, efficient caching and scalability via distribution over shards. We demonstrate how SIREn can effectively answer queries over 10 billion triples on single commodity machine. The prototype is currently in use in the Sindice search engine which index at the present time more than 50 million harvested documents containing semi-structured data.