Lofgren says that she is aware of the efforts of some of her committee colleagues to open impeachment hearings on Cheney. She does not say she is joining them. Instead she urges Chairman Conyers to reissue a report on impeachment produced by the committee in 1974 and to open hearings on that report. She writes that she wants the whole committee to have a common understanding of impeachment before beginning hearings. The report is titled "Constitutional Grounds for Presidential Impeachment".
Lofgren has issued a press release on the topic.
She has posted a PDF of her letter to Conyers.
She has also posted a PDF of the 1974 report "Constitutional Grounds for Presidential Impeachment".
Were Congresswoman Lofgren to support opening impeachment hearings for Cheney, she would be the 10th member of the Judiciary Committee to do so. There are 23 Democrats on the committee. Details on where each members stands can be found at http://afterdowningstreet.org/judiciarycommittee