After years of declining investments, venture capital (VC) firms have begun pumping money into start-up high-technology companies, according to different surveys.

The MoneyTree Survey, released Monday, reported that nearly $21 billion was invested in start-up and emerging companies in 2004. The survey was prepared by the PricewaterhouseCoopers accounting firm, Thomson Venture Economics, and the National Venture Capital Association.

VC investments had declined to the $18.9 billion invested in 2003, according to the MoneyTree survey, which noted that 2004 was the first increase in VC investing since 2000--the year the telecommunications and high-technology bubble began deflating.

The findings of another survey, released Friday by Ernst & Young/Venture One, also observed that VC investing in technology firms was rising for the first time in years, and some observers said the return to the positive investing climate was due in part to rises in the stock market in recent months. Another factor cited was the successful Google IPO, which illustrated to many that technology investments were returning to normal.

The Ernst report placed VC investing in technology companies at $11.3 billion last year. (The two surveys look at high-tech venture investing from different perspectives.) Ernst said software investments--the biggest piece of the technology venture market--were up 19.5 percent, to $4.9 billion in 2004. The survey reported that communications and semiconductor investments, however, fell 17 percent, to $2.5 billion.

The MoneyTree report broke out investments on a regional basis, noting that Silicon Valley remained in first place in 2004 as far as investment dollars received; the Boston area finished in second place.

MoneyTree reported that VoIP provider Vonage Holdings raised some $145 million in two venture rounds in 2004.